The present invention relates to an electroless gold plating solution and a method for plating gold using the same.
The conventional electroless gold plating solutions are composed primarily of potassium gold (I) cyanide, potassium cyanide and a borane-based compound as reducing agent as described, for example, in Plating, Vol. 57 (1970), pp. 914-920. This process can produce a plating solution capable of exhibiting a plating rate of 1 .mu.m/hr. U.S. Pat. No. 3,506,462 discloses those composed of potassium gold (I) cyanide and thiourea as a reducing agent.
On the other hand, Japanese Patent Publication No. 56-20353 discloses a cyanide ion-free electroless gold plating solution comprising primarily chloroaurate (III) and hydrazine as a reducing agent.
The prior techniques as described above have caused problems that as the reducing agents are consumed, the reaction products thereof are accumulated to inhibit the plating reaction, and that the stability of the solution is significantly reduced due to the reduction reactions of gold ions with the reaction products in the solution.